People gather around a car as it is removed by a mobile crane in Tehran, Iran. The car was being driven by Iranian nuclear scientist Mostafa Ahmadi Roshan when it was targeted by a bomb Wednesday. Roshan was killed in the blast.
Meghdad Madadi/AP
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Meghdad Madadi/AP

People gather around a car as it is removed by a mobile crane in Tehran, Iran. The car was being driven by Iranian nuclear scientist Mostafa Ahmadi Roshan when it was targeted by a bomb Wednesday. Roshan was killed in the blast.

Meghdad Madadi/AP

Earlier this week, 32-year-old nuclear scientist Mostafa Ahmadi Roshan was killed by a bomb blast on his way to work in Tehran, Iran.

The attack, carried out with a magnetic bomb placed on Roshan's car by a man on a motorcycle, was like something out of a spy novel. In Iran, however, it's very much a reality. Assassins have targeted five Iranian nuclear scientists in the past two years; four of the attacks have succeeded.

Iran accused Israel of being behind the attack, but Israeli President Shimon Peres denied the nation was involved. Either way, the assassination has contributed to growing tensions between Iran and the West, and the gathering storm over the nation's nuclear ambitions and oil supply.

Line In The Sand

About a fifth of the world's oil supply comes through the Strait of Hormuz, a narrow channel that connects the Persian Gulf to the Arabian Sea. Some officials in Iran have threatened to block it if the United States manages to convince other countries to stop buying Iranian oil.

Late this week, the Obama administration sent Iran a clear message that the blockade of the strait would be a red line. Ambassador Dennis Ross, who until recently was the administration's top adviser on Iran, tells weekends on All Things Considered host Guy Raz that talk of "red lines" generally precludes a military response should that line be crossed.

International pressures in the form of multiple U.N. Security Council sanctions and talk of Europe boycotting Iran's oil is putting Iran in a bind, Ross says.

"Oil basically accounts for close to 90 percent of the government's revenue. When you're looking at that from their standpoint, and you're under greater isolation than you have ever been before, it's not surprising that there is a strong rhetorical response by them. One can't dismiss and assume that rhetoric is only going to be all they do, but I think by the same token we should also put what they're saying in some perspective."

Ross says the idea behind the sanctions is to put pressure on Iran and to let the country know that its actions have consequences. A year ago, Iran's President Mahmoud Ahmadinejad scoffed at the sanctions, Ross says. Now that Iran is feeling the economic pressures, he says, that creates a greater potential for a diplomatic solution to succeed.

More U.S-Iran Unease: Why Now?

With all of the hits to Iran's nuclear program -– assassinations, sanctions, 18 suspicious explosions in 2011, the Stuxnet virus — Trita Parsi, a scholar who heads the National Iranian-American Alliance, tells Raz that the interesting question to ask is: Why hasn't Iran acted out?

"One possible explanation as to why they haven't is that they view this potentially as a trap; that there is an effort by some state in the region, perhaps Israel, wanting the Iranians to retaliate, and by that give a pretext for a larger war. As a result, the Iranians are in an odd way showing a lot of restraint."

The upcoming P5+1 talks (named for the five members of the U.N. Security Council plus Germany, who are to sit down with representatives from Iran) are scheduled to take place later this month. Parsi says the two sides have escalated things right before upcoming negotiations in order to maximize their bargaining power.

The threat of closing the Strait of Hormuz, in an election year focused on the economy, is part of that jockeying for position, Parsi says.

Parsi agrees with Ross that Iran is feeling the pressure from the sanctions, but the U.S. should not pat itself on the back just yet and Iran might still have some cards to play.

"We haven't seen much of the cost of [the sanctions] yet because they really haven't played those cards," Parsi says.

Correction April 17, 2012

A previous version of this post mistakenly said "G5+1" in reference to the talks. They are the "P5+1" talks. The "P5" are the permanent members of the U.N. Security Council. The "+1" is Germany. Those six nations are, as a group, negotiating with Iran.